The present invention relates generally to voltage regulators.
Voltage regulators, such as DC to DC converters, are used to provide stable voltage sources for electronic systems. Efficient DC to DC converters are particularly needed for battery management in low power devices, such as laptop notebooks and cellular phones. Switching voltage regulators (or simply xe2x80x9cswitching regulatorsxe2x80x9d) are known to be an efficient type of DC to DC converter. A switching regulator generates an output voltage by converting an input DC voltage into a high frequency voltage, and filtering the high frequency voltage to generate the output DC voltage. Specifically, the switching regulator includes one or more switches to alternately couple and decouple an unregulated input DC voltage source, such as a battery, to a load, such as an integrated circuit. An output filter, typically including an inductor and a capacitor, is coupled between the input voltage source and the load to filter the output of the switch and thus provide the output DC voltage. A controller, such as a pulse width modulator or a pulse frequency modulator, controls the switches to maintain a substantially constant output DC voltage.
There is a shift to smaller inductors in switching regulator filters in order to increase switching regulator speed. Unfortunately, one problem is that the impedance of the filter elements in the switching regulator is becoming so small that parasitic impedance, e.g., parasitic inductance in the connection elements between the voltage regulator and the load, can adversely affect the switching regulator performance. A typical connection between the switching regulator and load can include a first socket in which the switching regulator is mounted, a second socket in which a processor or memory chip is mounted, and a trace between the first and second sockets. Each of these elements contributes to the parasitic inductance of the connection. When the parasitic inductance of the connection is combined with the input capacitor in the load and the filter capacitor in the switching regulator, a CLC network can be formed. This CLC network is a source of instability in the switching regulator performance.
In addition, the drive to high performance computers will result in devices that require faster shifts and shifts of larger magnitude in the load current. Consequently, switching regulators with higher reaction speed to changes in the load current will be needed.
In one aspect, the invention is directed to a voltage regulator having an input terminal, an output terminal, a first transistor to intermittently form an electrical circuit between the input terminal and the output terminal, a rectifier connecting an intermediate terminal in the electrical circuit between the input terminal and the output terminal to ground, a controller that drives the first transistor, and a capacitorless filter. The capacitorless filter includes an inductor connected between the intermediate terminal and the output terminal.
Implementations of the invention may include the following features. The rectifier may include a second transistor, and the controller may drive the first and second transistors to alternately couple the intermediate terminal between the input terminal and ground. The first transistor may be a PMOS transistor, and the second transistor may be an NMOS transistor. The voltage regulator may be a buck converter, a boost converter, or a buck-boost converter.
In another aspect, the invention is directed to an electronic device that includes a voltage regulator and a load. The voltage regulator has an input terminal to couple to a voltage source and an output terminal, a first transistor to intermittently form an electrical circuit between the input terminal and the output terminal, a rectifier coupling an intermediate terminal in the electrical circuit between the input terminal and the output terminal to ground, a controller that drives the first transistor, and a capacitorless filter including an inductor coupled between the intermediate terminal and the output terminal. The load has elements coupled to the output terminal and an input capacitor between the output terminal and ground. In conjunction with the inductor of the voltage regulator, the input capacitor provides a filter so that the voltage to the elements of the load remains substantially constant.
Implementations of the invention may include the following features. At least a portion of the voltage regulator may be fabricated on a first chip and at least a portion of the load may be fabricated on a second chip. The first and second chips may be mounted on a printed circuit board, and the input capacitor may be mounted on the printed circuit board. The first chip may be mounted on a first printed circuit board, the second chip may be mounted on a second printed circuit board. The first printed circuit board may be mounted on the second printed circuit board, or the second printed circuit board may be mounted on the first printed circuit board, or the first and second printed circuit boards may be mounted on a third printed circuit board. The input capacitor may be mounted on the first printed circuit board, the second printed circuit board or the third printed circuit board, or fabricated in the second chip.
In another aspect, the invention is directed to an electronic device that has a voltage regulator, a load and a capacitor. The voltage regulator includes an input terminal to couple to a voltage source and an output terminal, a first transistor to intermittently form an electrical circuit between the input terminal and the output terminal fabricated on a plurality of first integrated circuit (IC) chips, a rectifier coupling an intermediate terminal in the electrical circuit between the input terminal and the output terminal to ground, and a controller that drives the first transistor. The load is fabricated at least partially on a second integrated circuit (IC) chip that receives power from the output terminal of the voltage regulator. The capacitor is located near the second IC chip that provides the necessary capacitance to filter current entering the load and create a substantially DC voltage at the load.
Implementations of the invention may include the following features. The plurality of first IC chips may be located on a first printed circuit board and the second IC chip may be located on a second printed circuit board. A current summing node to sum current from the plurality of first IC chips may be located on the first printed circuit board, or the current summing node can be located off the first printed circuit board.
In another aspect, the invention is directed to an electronic device that has a voltage regulator, an electrical connector having a parasitic inductance, and a load. The voltage regulator has an input terminal to couple to a voltage source and an output terminal, a first transistor to intermittently form an electrical circuit between the input terminal and the output terminal, a rectifier coupling an intermediate terminal in the electrical circuit between the input terminal and the output terminal to ground, and a controller that drives the first transistor. The load has active elements coupled by the electrical connector to the output terminal, the load further including an input capacitor between the output terminal and ground, wherein in conjunction with the parasitic inductance of the electrical connector, the input capacitor provides a filter so that the voltage to the active elements of the load remains substantially constant.
Implementations of the invention may include the following features. At least a portion of the voltage regulator may be fabricated on a first chip and at least a portion of the load may be fabricated on a second chip. At a least a portion of the parasitic inductance may be provided by traces on a printed circuit board. The second chip may be mounted on a printed circuit board, and at least a portion of the parasitic inductance may be provided by a connector between the second chip and the printed circuit board. The first chip may be mounted on a first printed circuit board, the second chip may be mounted on a second printed circuit board, and at least a portion of the parasitic inductance may be provided by a connector between the first and second printed circuit boards.
In another aspect, the invention is directed to an electronic device that has a voltage regulator, a load and a capacitor. The voltage regulator has an input terminal to couple to a voltage source and an output terminal, a first transistor to intermittently form an electrical circuit between the input terminal and the output terminal fabricated on a first integrated circuit (IC) chip that is mounted on a first printed circuit board, a rectifier coupling an intermediate terminal in the electrical circuit between the input terminal and the output terminal to ground, and a controller that drives the first transistor. The load is fabricated at least partially on a second integrated circuit (IC) chip that is mounted on a second printed circuit board, and the load receives power from the output terminal of the voltage regulator. The capacitor is located on the second printed circuit board and provides, in conjunction with inductance located between the input node and the load, a filter that creates a substantially DC voltage at the load.
Implementations of the invention may include the following features. The controller may be at least partially fabricated on a third integrated (IC) circuit chip. The capacitor may be an input capacitor for the second IC chip. The capacitor may be selected to ensure that the input capacitor can effectively shunt sufficient current that the voltage across the load remains substantially constant. The inductance may be provided by an inductor coupled between the input terminal and the output terminal of the switching regulator, and the inductor in the filter may be supplemented by a parasitic inductance in a connection between the output terminal and the local capacitor. The inductance may be provided by a parasitic inductance in a connection between the output terminal and the local capacitor. The parasitic inductance may occur in a connection between the second IC chip and the second printed circuit board, in a connection between the first IC chip and the first printed circuit board, or in a connection between the first printed circuit board and the second printed circuit board.
Advantages of the invention may include the following. The capacitive elements of the switching regulator filter, i.e., the output capacitor elements, can be located entirely on the motherboard, on a peripheral board on which the load chip is mounted, or in the load chip itself. This reduces the parasitic impedance between the capacitors and the load, thereby enhancing the speed with which the switching regulator can react to changes in the load current. By eliminating the filter capacitor from the voltage regulator side, creation of a CLC network can be avoided, and the stability of the switching regulator can be improved. In addition, the feedback control path can be simpler and more stable. The switching regulator and load can be located in different modules separated by sockets. All of the output capacitance elements may be located in the load module, and can be very close to the load in order to filter out very fast current transients. The switching regulator can be manufactured at lower cost by placing the capacitance at the load.